The present invention relates to a semiconductor chip, a semiconductor integrated circuit device, and a method of manufacturing semiconductor integrated circuit devices, and particularly to a technique useful for the manufacturing of nonvolatile memories of the type of block-erasure.
EEPROM of the type of electrical block erasure is a nonvolatile memory device having a function of erasing at once all memory cells or a block of memory cells formed on a semiconductor chip. The electrically block erasing EEPROM has a memory cell structure which resembles that of ordinary EPROM. Specifically, a memory cell is formed of an insulated gate field effect transistor having a double-layer structure (will be termed “MOSFET” or simply “transistor”), which stores data virtually in terms of the variation of threshold voltage. The data write operation of the memory cell is identical to EEPROM.